Actually, I kind of agree with Raven here. Turning Castle into a 3 gives up the majority of his physical advantage. That will reduce his value as a player (and his career earnings, awards, etc). It's much more optimal for both team and player for Castle to develop into a 1 (or at least a two)... Yes this development process will be painful. But given his work ethic, and his demonstrated ability to see good passes, I think he will get there (just like TP9 did, it just took several years and lots of reps).
In the meanwhile, were I running the team, after the all-star break, I would make Fox the primary ball handler in the starting line-up, to ramp up for the play-offs...